I have FreeBSD 7 and install Qemu from port and run FreeBSD 7 with Qemu
so I have FreeBSD 7 in Qemu
I want ssh from OpenBSD box to FreeBSD box run in qemu
My IP in OpenBSD 4.2 is 192.168.0.50 with netmask 255.255.255.0
and IP in FreeBSD 7 is 192.168.0.51 with netmask 255.255.255.0
and IP in FreeBSD run in Qemu is 10.0.2.15 , and I use DHCP for give IP to FreeBSD 7 run in Qemu

So I want ssh from my OpenBSD box to FreeBSD run in Qemu
what I must do ???

The default networking configuration for QEMU sets up a pure userspace network stack, using the SLIRP protocol for outbound TCP traffic to the host. This does not, however, allow for UDP traffic or any incoming TCP connections.

Qemu, like VirtualBox, does NAT by default. This means that the virtual machine will have an addresss of 10.2. x.x.
Ping and UDP don't work.
Maho's document is VERY dated, and various threads on the emulation list suggest that it be removed as a source.
If you look at /usr/ports/qemu/pkg-message, you'll see that Juergen has a link to my howto on bsdnexus. However, I haven't tried it in a long time, and it may no longer work. (Nor can I help, as these days I use Linux for a host system, as it can use KVM-Qemu, VMware server and VirtualBox.)

I don't know of any more current bridging howtos for FreeBSD, though one is probably necessary now. Mine was written when 7.0 was CURRENT, and some things may have changed. However, the basic concepts would still be there.